REGULATION - REGULATORY ASSETS AND LIABILITIES (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Sep. 30, 2022
Regulatory Assets And Liabilities [Line Items]
Regulatory assets-current	$ 61,355	$ 40,086
Total current regulatory liabilities	49,382	31,090
Regulatory liabilities-noncurrent	184,740	185,634
NJNG
Regulatory Assets And Liabilities [Line Items]
Regulatory assets-current	61,355	40,086
Regulatory assets-noncurrent	490,534	495,300
Total current regulatory liabilities	42,926	25,779
Regulatory liabilities-noncurrent	184,740	185,634
NJNG | Total current regulatory liabilities
Regulatory Assets And Liabilities [Line Items]
Total current regulatory liabilities	42,245	17,807
NJNG | Derivatives at fair value, net
Regulatory Assets And Liabilities [Line Items]
Total current regulatory liabilities	681	7,972
Regulatory liabilities-noncurrent	0	116
NJNG | Tax Act impact
Regulatory Assets And Liabilities [Line Items]
Regulatory liabilities-noncurrent	184,112	185,367
NJNG | Other noncurrent regulatory liabilities
Regulatory Assets And Liabilities [Line Items]
Regulatory liabilities-noncurrent	628	151
NJNG | New Jersey Clean Energy Program
Regulatory Assets And Liabilities [Line Items]
Regulatory assets-current	14,090	15,697
NJNG | Conservation Incentive Program
Regulatory Assets And Liabilities [Line Items]
Regulatory assets-current	19,633	23,099
NJNG | Derivatives at fair value, net
Regulatory Assets And Liabilities [Line Items]
Regulatory assets-current	26,314	0
NJNG | Other current regulatory assets
Regulatory Assets And Liabilities [Line Items]
Regulatory assets-current	1,318	1,290
Regulatory assets-noncurrent	39,249	45,828
NJNG | Expended, net of recoveries
Regulatory Assets And Liabilities [Line Items]
Regulatory assets-noncurrent	65,671	66,149
NJNG | Liability for future expenditures
Regulatory Assets And Liabilities [Line Items]
Regulatory assets-noncurrent	125,727	127,070
NJNG | Deferred income taxes
Regulatory Assets And Liabilities [Line Items]
Regulatory assets-noncurrent	40,732	40,520
NJNG | SAVEGREEN
Regulatory Assets And Liabilities [Line Items]
Regulatory assets-noncurrent	54,909	52,690
NJNG | Postemployment and other benefit costs
Regulatory Assets And Liabilities [Line Items]
Regulatory assets-noncurrent	55,972	56,021
NJNG | Deferred storm damage costs
Regulatory Assets And Liabilities [Line Items]
Regulatory assets-noncurrent	1,629	2,172
NJNG | Cost of removal
Regulatory Assets And Liabilities [Line Items]
Regulatory assets-noncurrent	106,645	104,850
Adelphia
Regulatory Assets And Liabilities [Line Items]
Regulatory assets-noncurrent	5,316	5,366
Total current regulatory liabilities	$ 6,456	$ 5,311